玉米秸秆集中深还田对旱地土壤CO2排放特征的影响

Effects of Corn Straw Concentrated Deep Returning on Soil CO2 Emission in Dry Land

摘要:

为探究秸秆深还条件下不同还田量对土壤CO₂排放的影响，于田间微区试验设置3个处理，分别为CK(无秸秆还田)、T1(全量还田，10 500 kg/hm²)、T2(倍量还田，21 000 kg/hm²)，通过LI-8100A土壤碳通量自动测定仪测定土壤CO₂排放速率并探究其影响因素。结果表明：①秸秆还田提高了CO₂排放速率，其中倍量还田与全量还田的CO₂累积排放量明显大于无秸秆还田(P<0.01)，分别增加了92.53% 和61.95%；②各处理CO₂排放速率在土壤温度为30 ℃、24% 含水量时达到最大，且土壤温度与水分的双因素拟合模型相较于单因素模型更好(R²为0.488 ~ 0.583)，说明CO₂排放速率受土壤温度和水分共同调控；③还田100 d后秸秆干物质残留量为25.54% ~ 28.21%，其腐解程度与CO₂累积排放量显著正相关，且秸秆腐解后，增加了土壤有机碳、微生物生物量碳、有效磷、速效钾含量，促进了CO₂排放。综上所述，土壤CO₂排放特征受土壤温度、含水量及其他土壤养分共同作用，且秸秆还田量的增加，能够提升土壤养分，增加CO₂排放，促进土壤呼吸。

Abstract:

In order to investigate the effects of different amounts of straw returned to the field on soil CO₂ emission under deep returning condition, an field micro-area experiment was conducted, in which 3 treatments were set, namely CK (no straw returned), T1 (full straw returned, 10 500 kg/hm²), and T2 (double straw returned, 21 000 kg/hm²), soil CO₂ emission rate was measured by LI-8100A automatic soil carbon flux analyzer, and its influencing factors were investigated. The results showed that: 1) Straw returning significantly increased CO₂ emission rate, with the cumulative CO₂ emissions from double and full straw returning significantly higher than those from no straw returning (P<0.01), which increased by 92.53% and 61.95%. 2) CO₂ emission rates reached the maximum at 30℃(temperature) and 24% (moisture) under all treatments, and the two-factor fitting model of temperature and moisture was better (R² = 0.488-0.583) than the single-factor model, indicating that CO₂ emission rate was jointly regulated by temperature and moisture. 3)The residual dry matter of straw was 25.54%-28.21% after 100 d of field return, and its degree of decomposition was significantly positively correlated with the cumulative CO₂ emission. The decomposition of straw increased soil organic carbon, microbial biomass carbon, available phosphorus and potassium contents, which promoted CO₂ emission. In conclusion, the characteristics of soil CO₂ emissions are affected by soil temperature, moisture and other nutrients, and the increase of straw returned to the field can promote soil nutrients, CO₂ emission and soil respiration.